Neither a history of light or moderate alcohol use nor acute doses of ethanol (0.35 or 0.7 g/kg) altered the abuse liability of 30% nitrous oxide in healthy light and moderate drinkers. Choice of nitrous oxide was similar across groups and ethanol doses, averaging about 3.3 out of 6 choices. Subjective effects like liking and desire to inhale the drug again were positively correlated with choice, but these effects were also unaffected by ethanol history or pretreatment. The findings suggest that, under these experimental conditions, ethanol does not modulate the reinforcing or subjective effects of nitrous oxide.
The reinforcing and subjective effects of nitrous oxide varied more between people than within the same person across sessions. Twelve volunteers without drug dependence inhaled 30% nitrous oxide or 100% oxygen for 10 minutes each, then chose between the two or drug-free air nine times per session. Choice differed across subjects but stayed stable within subjects. Some subjective effects correlated with choice and differed between consistent choosers of nitrous oxide and non-choosers, but drug liking and euphoria—standard measures of abuse liability—were unrelated to choice. Subjective effects fluctuated across sessions more than reinforcing effects did, underscoring the need for multiple measures when assessing abuse liability.